1. Field of the Invention
The present invention relates to the field of magnetic data recording. More particularly, the present invention relates to an apparatus and a method for improving data recording performance of a magnetic storage device at high data rates.
2. Description of the Related Art
A write driver (WD) in a magnetic storage device is a circuit that bi-directionally drives a write current through a write head for recording data on magnetic media, such as a magnetic disk. FIG. 1 shows an exemplary disk drive system 10 having a magnetic read/write head 11 that is positioned over a selected track on a magnetic disk 12 for recording data.
One impediment for improving performance of magnetic data recording at high data rates, that is, the speed at which data is written to a magnetic medium, is that the flux reversal time for a transition is slowed by eddy current damping in the core of the write head.
Another impediment for improving performance of magnetic data recording are parasitic capacitances that are associated with silicon devices of the write driver, the inductance and the parasitic capacitance of the write head and the losses due to the interconnect between the write driver and the write head that cause the rise and fall times of the write-current transitions through the write head to increase, thus degrading the performance of the write driver. FIG. 2 is a schematic block diagram showing a parasitic capacitance C.sub.D associated with a write driver WD, an inductance L.sub.H, a resistance R.sub.H and a parasitic capacitance C.sub.H associated with the write head, and an interconnect modelled as a transmission line by the distributed network consisting of the inductances L.sub.I and the capacitances C.sub.I between the write driver WD and the write head. The rise and fall times of the write-current transitions are slowed because the write current I.sub.W from the write driver must pass through the network shown in FIG. 2, which essentially forms a low-pass filter, to reach the write head.
The rise- and fall-time increase also degrades data-recording performance by causing nonlinear transition shift (NLTS) effects during write-current transitions and slowing the field transitions in the magnetic field at the pole tips of the write element.
A conventional write driver is typically configured to have current-switching H drivers, such as FET drivers, differential amplifier drivers and current-mirroring H drivers. Such a conventional configuration has a limited current output capability. Consequently, a conventional write driver has limited capability for compensating for the increase in flux reversal time caused by eddy current damping in the write head, the parasitic capacitance associated with the silicon devices of the write driver, the write head impedance and the interconnect losses between the write driver and the write head.
What is needed is a technique that compensates for eddy current dampening effects in the core of a write head, while also compensating for the parasitic capacitance associated with the silicon devices of the write driver, the write head impedance and the interconnect losses between the write driver and the write head to speed up the flux reversal time.